Silicon carbide coating of nitinol stents to increase antithrombogenic properties and reduce nickel release.
BACKGROUND
The use of stents in the superficial femoral artery is still limited by the number of restenoses. Influencing factors include thrombus formation and smooth muscle cell proliferation as well as motion stress. A reduction of thrombogenicity can be achieved by passive coating with silicon carbide, which induces less thrombus formation due to its semiconducting properties.


METHODS
Self-expanding peripheral stents with and without silicon carbide coating were examined in a chandler loop model. Assessed parameters included thrombocyte count, beta-thromboglobulin (TG), thrombin-antithrombin (TAT) III complex, and polymorphonuclear elastase. Nickel release was quantified at Days 1, 3, and 223 using graphite furnace atomic absorption spectrometry. To visualize thrombus formation on the surface, scanning electron microscopy was conducted.


RESULTS
The tests showed a superiority of the coated stents regarding beta-TG (484.0+/-180.2 IU/l vs 2189.1+/-898.9 IU/l) as well as formation of TAT III complex (16.0+/-19.1 microg/l vs 458.3+/-761.0 microg/l). Scanning electron microscopy revealed a nearly absent thrombus formation on the coating. Nickel release was reduced by more than 90% at all time points.


CONCLUSIONS
In the provided in vitro setting, silicon carbide coating applied to self-expanding peripheral stents showed an advantage regarding thrombogenicity. The passive barrier resulted in a limited release of nickel from the alloy itself. These features seem promising for the use in the peripheral vasculature.
Schmehl
Jörg M
JM
Department of Diagnostic Radiology, University Hospital of Tuebingen, D-72076 Tuebingen, Germany. joerg.schmehl@med.uni-tuebingen.de
Harder
Claus
C
Wendel
Hans P
HP
Claussen
Claus D
CD
Tepe
Gunnar
G
D000497:Alloys / Q000737:chemistry; D000990:Antithrombin III; D001777:Blood Coagulation / Q000187:drug effects*; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D017554:Carbon Compounds, Inorganic / Q000737:chemistry / Q000494:pharmacology*; D020099:Coated Materials, Biocompatible; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D019272:Leukocyte Elastase / Q000097:blood; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry; D010447:Peptide Hydrolases / Q000097:blood; D011474:Prosthesis Design; D017655:Silicon Compounds / Q000737:chemistry / Q000494:pharmacology*; D012995:Solubility; D013054:Spectrophotometry, Atomic; D015607:Stents; D013499:Surface Properties; D001620:beta-Thromboglobulin / Q000378:metabolism
D000497:Alloys; D017554:Carbon Compounds, Inorganic; D020099:Coated Materials, Biocompatible; D005343:Fibrinolytic Agents; D017655:Silicon Compounds; C046193:antithrombin III-protease complex; D001620:beta-Thromboglobulin; C013616:nitinol; D009532:Nickel; D000990:Antithrombin III; D010447:Peptide Hydrolases; D019272:Leukocyte Elastase; C022088:silicon carbide